Investigating the effect of H+-ion irradiation on layered α-MoO3 flakes by defect engineering.

Ion irradiation is a versatile and convenient tool for modifying the optical, electrical, and catalytic properties of two-dimensional (2D) materials through controlled induction of impurities and defects. The behavior of 2D materials under ion irradiation is interesting, which needs to be explored in the contest of their optoelectronic applications. In the present work, we have reported the effect of H⁺-ion irradiation on layered α-MoO₃ flakes by defect engineering. Initially, the α-MoO₃ crystals were synthesized using the physical vapor deposition technique followed by mechanical exfoliation of an as-grown crystal to obtain α-MoO₃ flakes of different thicknesses. Then, the exfoliated flakes were exposed to H⁺-ion/proton irradiation with a fluence of 1 × 10¹⁶ ions/cm² using a 30 keV source. After irradiation, new photoluminescence (PL) emission peaks were observed at different positions in the range of ∼2.4–1.9 eV, which was found to be absent in pristine flakes. Raman studies revealed non-uniform oxygen vacancy distribution in H⁺-ion irradiated α-MoO₃ flakes, which affected the PL peak positions. Additionally, first-principle calculations and Bader charge analysis were performed to identify the origin of the new PL peaks. Our findings indicate that oxygen vacancies positioning at different locations of the α-MoO₃ lead to the emergence of new absorption peaks within the range of ∼2.2–1.25 eV, which is consistent with our experimental findings. The present study gives insight into exploring the use of ion-irradiated α-MoO₃ in optoelectronics applications with tunable properties. [ABSTRACT FROM AUTHOR]